Such a combination is shown in Austrian Pat. No. 322 186. However, this patent does not describe a device which would also bring the outer flanges of the frames into alignment. However, such a device is shown in German Offenlegungsschrift (printed publication of an unexamined patent) No. 20 49 245. But in the device shown there the ribs do not come into contact with each other either when the steel frames are in the locked or unlocked state.
The combination described in the Austrian patent has the following disadvantages:
(a) The form panels are not aligned until the combination is set in place. Alignment is achieved by driving in a wedge. The resulting forces act to compress a plastic spacer sleever. However, the latter sleeves are usually made of plastic and do not stand up up to such forces. This means that one must try beforehand to align the form panels.
(b) The number of tie bolts used to join two form panels together depends on the number of aligned transverse holes provided in the steel frames. However, if a large number of holes are provided this weakens the frames. The tie bolts cannot perform any alignment because they cannot exert any force in a direction perpendicular to the plane of the form panels.
(c) It is not possible to produce a combination of forms in which the form panels can be offset in height in relation to each other by any desired amount.
(d) Combinations of form panels often consist of an entire unit pre-assembled on the ground which has to be lifted into the correct position by a crane. Because of the hitherto available form lock devices such a combination is very unstable and has to be handled carefully. When the combination of forms is then placed against the wall to be poured, it has to be adjusted, i.e. the form panels have to be aligned.
(e) If the sectional steel frame of the form is hollow, the holes in its flanks have to be plugged to prevent any concrete flowing in. These are all additional work steps.
(f) The holes in the flanks dictate at what points the forms can be locked, although these points may not always be the optimum ones at which to position the locks.
(g) In the known type of combination of forms, the initially established flush alignment may be lost when the tie rods, which are always present, are tightened.
(h) The combination of forms is difficult to produce because the wedges are hard to reach to knock them in. If one is not careful, it is possible to hit the sectional steel frame because the wedges are located close to the frame, and what is more they are located at those parts of the frame which form a corner with the form panel. In practice, therefore, the lock elements are positioned in such a way that the wedges run at an angle from top front to bottom rear. This means, however, that when the wedges are removed again there is practically no room for the hammer to be used, because the tip of the wedge is even more inaccessible than the head.